The present invention relates to mounting systems for mounting electrical connectors on a printed circuit board and, more particularly, to mounting system which allow a measure of relative movement between the connector and its printed circuit board.
One of the trends in the manufacture of electronic systems is to provide a backplane or `motherboard` in which a number of `daughterboards` are connected to form a complete system. This approach allows the system designer to place as many electrical devices and circuits as is practical on the daughterboards to maximize packaging efficiency and to shorten on-site service and repair time to that required to remove a defective daughterboard and replace it with a functional board. In larger systems, the size of each daughterboard can be quite large, for example, up to 24 inches (30 cm.) on a side. In such systems, a large number of circuit interconnects must oftentimes be effected with the motherboard. To this end, high pin count connectors systems have been developed which locate the respective pins and receptacles on relatively close centers, for example, 0.100 inches (2.54 mm.) in a multi-row matrix so that several hundred or more circuit connects are possible per connector.
In general, the use of a high pin count connector does not entail special mounting considerations. However, where the circuit board is relatively large and the number of circuit connects requires the use of two or more separate connectors along an edge of the printed circuit board, problems can be encountered under certain circumstances when mating the printed circuit board to its motherboard. For example, when the system is initially assembled, the daughterboards are typically at the same temperature as the motherboard and insertion of the daughterboards into their connectors on the motherboard is accomplished in the usual manner. Once the system is powered-on, the heat energy developed as a consequence of operation of the circuits causes the motherboard and the daughterboard to physically expand. Thus, where the daughterboard has two or more connectors along the edge that mates to the motherboard, the spacing between the connectors is increased somewhat. In general, this thermal expansion does not pose a problem or introduce undue physical stresses, since the various boards and connectors are made from the same materials or materials that are reasonably compatible with each other. However, if it is necessary to remove and replace a thermally hot daughterboard with replacement daughterboard that is at room temperature, the difference in physical size and connector spacing can greatly increase the insertion force, particularly where small pin center dimensions are used, and can unduly stress both the thermally hot motherboard and the room temperature daughterboard. While it is possible to allow the entire system to cool to room temperature before effecting board replacement, such a repair protocol is economically inefficient.